Gas cell fabric



Patented Feb. 23, 1932 mrso sures PATENT OFFICE W 0.. CALVERT, OF AKRON, OHIO, A8SIGLN'OB TO THE GOODYEAR TIRE BUB- EBKR COBIPANY, OF AKRON, OHIO, A

CORPORATION 01' OHIO GAS CELL FABRIC We thawing. Application fled-{April 8, is invention relates to coated fabrics and has particular relation to fabrics of the hind employed in the construction of .gas cells for lighter-than-aircraft. It is not, however, limited in its usefulness'to such gas cells, for it may he used wherever a fabric is desired possessing the properties characterizing the herein described material.

@ne object of the invention is to provide a fabric which-offers exceptionally high resistance to permeation by hydrogen and helium.

.dnother object of the invention is to provide a fabric which is exceptionally light of weight, durable and flexible.

ll third ohject is to provide a; fabric having the above designated characteristics, the units of which may be spliced together by means oi moisture-proof rubber cements.

Uther obiects will he apparent as the description of the invention proceeds.

For convenience; the invention will be descrihed hereinafter as applied to lighterthon-aircrait, but it will he understood that in loot not limited thereto, being capable heing put "to many other uses,

The gas cells oi lighter-than-aircra ft are usually constructed oilight, strong,closely oven cotton textile material'which iscoated 'th a continuous lilm oi a highly impervious designed to prevent unduly rapid dillusion oi the imprisoned gases. Although many materials have heretofore heen emved for coating these falorics, only two terials, ruhher and gold heater s skin, heretotlore heen considered to possess ill where is ahundant and relatively cheap ohtain and may also he applied to the isle by mechanical means with a minimum expenditure oi time "and labor. it is als'oimpermeuhle to moisture and units thereof may ruhher cements which are also not ofiect ed he equisite properties ilor extensive commereodily he secured together hy means .of-

1980. Serial Io. 44am.

by moisture. In these respects, rubber is al most an ideal material.- However, it is also subject to serious objections. For example, the permeability thereof is comparatively high and accordingly,-it is necessary to employ coating films of excessive thickness and weight in order to obtain sufiicient resistance tothe escape of the inflating gases. Furthermore, when it is spread in relatively thin films upon ordinary fabrics, it is subject to relatively rapid decay. Within a comparatively short time, itis likely to crack and check, thus leaving openings through which, the imprisoned gases may escape.

Gold beaters skin is obtained in the form of relatively small strips or units from the viscera of cattle. I It is necessary to subject it to tedious processing in order to obtain it inform suitable for application to fabric. The units thereof are applied to the fabric hy means of some convenient cement such asrubber or glue. Since these units are comparatively small in size, much time and labor is necessary in order to s read it upon such extensive surfaces as exist "in gas cells of lighter-than-aircraft. However, it is quite tough, flexible and afl'ords very high resistance to permeation by gases. In these respects,'it is markedly diflerent from the rub r coatings. In the construction of gas cells for rigid craft of the Zeppelin type, where it is necessary to imprison great quantities of gases over long periods of time, these advantages have been found to outweigh the disadvantages. Therefore, it has found extensive application in this type ofaircraft even though the expense of application is great.

llleretofore, much time and effort has been expanded in an edort to develop a synthetic material having the lightness and durability of old beaters skin which may be obtained and applied with an expenditure of etfort more nearly approximating that of rubber. Althou h numerous compositions such as nitroce ulose and other esters of cellulose have been suggested, none of themhas been found to be entirely practicable For example; some have been unduly permeable to inflating gases. As a specific example of this type of material, mention may be made of nitrocellulose which, although apparently extremely dense and-impermeable, is found by actual experience to permit the loss of fifteen liters of inflating gas per square meter of fabric. Furthermore, most of these compositions are objectionable because it is difficult by ordinary means to secure units thereof together by means of the common cements. Various other objectionable features such as inflexibility and lack of durability have also v been encountered in connection with some of the materials heretofore proposed.

The present invention consists in the proa vision of a composition consisting of gelatin, latex and a softening in edient such as polyglycerol applied to the abric'in such manner that substantially all of the objections here .tofore encountered in connection with gold beaters skin or rubber coatings for gas cell fabric are substantially overcome while the v advantages of both are retained.

In practicing the invention, a suitable gas cell fabric is preferably spread with a very thin light coating of rubber weighing approximately 0.8 ounces per square yard. This material may be spread upon a single side of the fabric, but it is preferable to apply it to both sides in order to reduce the tendency of the fabric to curve upon application, of solvents for purpose ofseaming the units of fabric together. This coating is then su'cceeded by a iSeCODd coating of self curing rubber cement which may have'the following "formula:

Percent by weight Rubber 4.9

Zinc oxide Sulfur Captax (mercaptobenzo thiazole) Diethylamine"; 0.047 Benzol i v q 34.840 Naphtha 59.780

The third coating consists of a of latex which 'may vary in composition but which preferably should contain approximately 67.5

vpercent of rubber. Additional coatings .comprising mixtures of gelatin, latex andpolyglycerol are then applied to the rubber base. In these coatings, the first plies are composed of relatively largepercentages oflatex and correspondingly small proportions of gelatin. However, the ratio of gelatin to latex is gradually increased in succeeding plies until eventually a number of plies of pure and nearly pure gelatin or polyglycerol are applied. The gelatin-polyglycerol coatings are 1 succeeded by a number of coatings of a gelatin, polyglycerol and latex mixture which readily adhere to the gelatin surfacceamost of the substitutes ployed. Solution A comprises Gr 5 Rubber latex (67.5% rubber) 150 Sodium hydroxide concentration) 7.5 Water 217.5

The composition of Solution B is as follows:

. Grams- Gelatin 200 Polyglycerol 450 Water n 1572 The exact order of application and composition of the variouscoatings may be tabulated .as follows:

Coat #1-Self curing rubber cement (containing sulfur and ultra accelerator e. g. mercaptobenzothiazole salt of diethyl amine) .05 Coat #2-Solution A. .10 Coat #3-80 grams Solution A, 120 I ams Solution B, grams water .07 Coat #4-40 grams Solution A, 240

' grams Solution B .05 Coats #518-Sol'ution B 1.00 Coat #1940 grams Solution A, 240

grams Solution B Coat #20-.40 grams Solution A, 240

grams-Solution B .05

Coat#21100 grams latex (67.5% rubbercontent) 93 grams water It is to be understood that each coating or film of material is permitted to dry before the succeeding coating is spread. It is also essential that the fabric be maintained under tension by suitable means such as stretching frames or other convenient devices in order to insure that it will be smooth and free from wrinkles. When properly prepared, gas cell fabrics of ordinary type, weighing approximately 2.8 ounces per square yard, are found to have a weight of approximately 4.22ounc'es per square yard. Such fabrics permit a diffusion of approximately .21 liters of hydrogen per square meter during a period of 24 hours. This loss is comparatively small, in fact, it is probably even less than that permitted by gold beaters skin.. The exterior latex coatings also function admirably as foundations for rubber cements which may be employed to bond the various units of fabric together. This is a distinct advantage over for gold beaters skin neaasoar heretofore suggested because the latter cannot be secured by means of such cements. Indeed, in connection with most of these materials, one of the most diflicult problems heretofore encountered has been to obtain an adequate seam for'the various units.

Although I have described the preferred embodiment of the invention, it will be apparent to those skilled in the art that it is not limited thereto but that various modifications may be made therein without departing from the spirit of the'invention or from the scope of the appended claims. It is intended that that the patent shall cover, by suitable expres sion in the appended claims, Whatever features of patentable novelty reside in the in-,

yention herein disclosed.

lFVhat I claim is: g p

1. A method of treating balloon fabric which comprises spreading thereon a coating of rubber, spreading latex upon the rubber,

then spreadinga coating of a mixture of; la ten and gelatin, adding intermediate coatings of gelatin and polyglycerol, applying a coating consisting of a mixture of elatin,

latex and polyglycerol and finally ad ing an exterior coating consisting essentially of later.

2. A. method of preparing balloon fabric which comprises coating a light strong closely Woven fabric base with a self curing rubber cement, spreading a coating of latexand gelatin upon the cement, addinga coating of a mixture of gelatin and polyglycerol followed by a coating of a mixture of latex gelatin and polyglycerol, and finally applying a coating consisting essentially of latex.

3. A gas cell for lighter-than-aircraft comprising a closely "woven cotton fabric base, a film of rubber upon the base, an intermediate film consisting essentially of gelatin and polyglycerol, and an outer ply consisting'esse ntially of rubber.

l, A method at manufacturing oated' fabrics which comprises coating a fabric base with rubber, spreading latex'uponrthe rubber, spreading a mixture of later: and ela tin upon the later, adding an interme late coating of gelatin and a softener, coating the gelation with a mixture of latex and gelatin,

gredients, and an outer layer consisting primarily of rubber, the latter layer being joined to the other unit by means of rubber cement;

7(A gas cell fabric for lighter-than-air craft comprising a baseof light textile material, inner and outer coatings consisting es the' fabric consisting essentially of rubber and an intermediate coatingcomprising gelatin and polyglycerol between the rubber coatings, the latter being blended in progressively decreasing proportions into the intermediate coatings.

9. A gas cell fabric for lighter-than-aircraft comprising a base of light fabric, inner antl outer coatings of rubber upon one side of the base, an intermediate coating comprising polyglycerol, and a medium highly resistant to permeation by hydrogen and he lium intermediate the rubber coatings.

10. A gas cell construction comprising a plurality of units of -fabric,each unit comprising inner and outer layers of rubber and intermediate layers of a material highly re; sistant to diffusion gases, the units being joined together by means of rubber cement.

In witnesswhereof, lhave hereunto signed my name. Signed at Akron, in the county of Summit and State of Ohio, ll S. A., this 7th day of April, 1930.

WlLlilAl/l C. CALVERT.

and finally dressing the latter coating with 5. A gas cell for lighter-than-aircratt corn-- prising a. closely woven cotton labricbase,

a film of rubber upon the base,'an intermediate film consistin of elatin and ol '1 c erol, and an outer coating. consisting essentially or rubber which is coated with paraffin or similar material. a

6. A gas cell construction for lighter-thanaircralt embodying a plurality of units of textile fabric, one out which at the line of union is coated with a la er comprising rubber as its principal in re ient, a layer comprising gelatin and po yglycerol as essential in- 

